Anthropic Launches Claude Fable 5.1 with 75% Cheaper Caching and Secure Mythos 5.1

9 月 2 日，Anthropic 正式发布 Claude Fable 5.1 与 Claude Mythos 5.1。Fable 5.1 是当前能力最强的模型升级版，专精复杂长时任务与科学研究；Mythos 5.1 与其同底层，但仅限受信任访问计划，面向网络防御与生命科学场景。新模型基准显著提升、缓存成本大降，并随 Claude Code 2.1.257 默认上线。

已确认

• 性能：Terminal-Bench-Science 0.1 得分 52.6%，为 Fable 5 的两倍多；Terminal-Bench 整体登顶；在较低努力层级下即可超过 Fable 5 的效果。
• 定价：输入/输出维持 $10/$50 每百万 Token；Prompt Cache 读取成本从 $1 降至 $0.25，降幅 75%。官方与 @kimmonismus、@markk 转述均确认典型工作负载成本约降 25%，重度缓存场景成本降幅约 45%（@drcintas 转述为 25%45%）。
• 可用性：已上线 Claude API 与应用；Claude Code v2.1.257 将其设为默认模型，支持 100 万上下文，并加强自动模式安全。
• 配套政策：发布同时重置所有用户的 5 小时与周使用限额（@thesaraharminta 转述）。
• 隐私与安全：引入企业级零留存防护等隐私安全升级（@claudeai）。

时间线

• 发布当日早些时候，@External-Grape-2978 等 Reddit 用户发现应用中悄然出现该模型，当时无官方公告与模型卡，Bedrock 标识符一度显示未找到；随后 Anthropic 官方正式宣布发布。

为什么重要

• 缓存降价 75% 对 Coding Agents 等长上下文重复利用场景影响最大，@markk 称这是最被低估的改进，可显著降低编程成本。
• 同一模型分「通用/受信」两档发布，体现了 Anthropic 对高危行业（网络防御、生命科学）采取差异化安全管控的产品策略。

2026-09-02 ~ 2026-09-02 · 33 related posts

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• [source] Anthropic releases Claude 5.1: 25% cheaper with zero-retention enterprise safeguards — claudeai · 2026-09-02
• Anthropic Launches Claude Fable 5.1 and Mythos 5.1 Models — AI_Andrew · 2026-09-02
• [source] Anthropic releases Fable 5.1 and Mythos 5.1 with major cost cuts — ClaudeOfficial · 2026-09-02
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• [source] Claude Code 2.1.257: Defaults to Fable 5.1, Hardens Auto Mode Security — ClaudeCodeLog · 2026-09-02
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6 near-duplicate retellings: scaling01 · TFenrir · Scobleizer · prasenx · aziz4ai · dr_cintas